Hydrogenolysis of Glycerol and Products Produced Therefrom

ABSTRACT

Processes for the hydrogenolysis of glycerol, as well as products produced therefrom are disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

The application claims the priority benefit under 35 U.S.C. § 119(e) toU.S. Provisional Patent Application No. 60/853,574, filed Oct. 23, 2006,the contents of the entirety of which is incorporated by this reference.

TECHNICAL FIELD

This invention relates to processes for producing polyhydric glycerolderivatives, as well as compositions obtained therefrom.

BACKGROUND

Catalytic hydrogenolysis (hydrocracking) of polyol is a process wherebypolyols such as sugars, glycerol and glycols are reacted with hydrogento produce other polyols. The polyols so produced often comprise amixture of several polyols having a lower average molecular weight thanthe starting material. The impurity of the polyol product mixture(derivatives) presents a problem for sale and use of the product.

The conversion of polyols such as sugars and glycerol to polyhydricalcohols such as propylene glycol and ethylene glycol by hydrogenolysisor by hydrocracking results in formation of not only these alcohols, butseveral other unwanted products, such as 1,2-butanediol, 1,3-butanediol,1,4-butanediol, 2,3-butanediol and 2,4-pentanediol. These products arerecovered with the propylene glycol and ethylene glycol. Due to thesimilarity in boiling points, these diols are very difficult to separatefrom propylene glycol by distillation. For instance, in hydrocracking ofhigher carbohydrates such as sorbitol to produce propylene glycol,typically 3-5% by weight of 2,3-butanediol is produced in addition to1,2-butanediol, ethylene glycol and 1,3-butanediol. Table 2 provides alist of polyols produced by hydrocracking of sorbitol as described inU.S. Pat. No. 4,935,102, which is incorporated herein by reference inits entirety. The boiling points of these components as shown in Table 1are very close to one another such that in a rectification column,either under atmospheric pressure, reduced pressure or at an elevatedpressure, the separation of substantially pure propylene glycol isdifficult to attain. TABLE 1 Polyols produced by Hydrocracking ofSorbitol (U.S. Pat. No. 4,935,102) Weight Boiling Point, CompoundPercent ° C. 2,3-Butanediol 3.5 182 Propylene glycol 16.5 1871,2-Butanediol 2.0 192 Ethylene glycol 25.2 198 1,3-Butanediol 2.7 2062,3-Hexanediol — 206 1,2-Pentanediol — 210 1,4-Pentanediol — 2201,4-Butanediol 2.1 230 1,5-Pentanediol 0.1 242 Diethylene glycol 2.2 2451,6-Hexanediol — 250 Triethylene glycol 2.1 285 Glycerol 38.8 2901,2,4-Butanetriol 4.8 190/18 mm 100.00

The differences in volatility of propylene glycol compared to2,3-butanediol and 1,2 butanediol are very small. As shown in Tables 2and 3, for separation of these compounds from a mixture by distillation,the number of plates required to achieve 99% purity is very large; thusvery tall distillation columns (55 trays for 2,3-Butanediol and 88 traysfor 1,2-Butanediol) and high energy inputs are required. TABLE 2Theoretical and Actual Plates Required vs. Relative volatility forPropylene Glycol - 2,3-Butanediol Separation. Actual Plates, 75%Relative Volatility Theoretical Plates Efficiency 1.25 41 55 1.35 31 421.45 25 34 1.50 23 31 1.70 18 24

TABLE 3 Theoretical and Actual Plates Required vs. Relative volatilityfor Propylene Glycol - 1,2-Butanediol Separation. Actual Plates, 75%Relative Volatility Theoretical Plates Efficiency 1.15 66 88 1.5 23 312.0 14 19 3.0 9 12 3.5 8 11

The processes involved in the hydrogenolysis of glycerol may be carriedout by any of the known routes. These include heterogeneous metalcatalysts, such as those described in U.S. Pat. No. 6,479,713, PCTpatent application WO 2005/051874, US patent application 2005/0244312 orreferred to in Catalysis Communications 6 (2005) 645-649 or Journal ofCatalysis 240 (2006) 213-221, each of the contents of the entirety ofwhich are incorporated herein by this reference. The processes alsoinclude homogenous catalysts as referred to in Hydrocarbon Processing(February 2006) pp 87-92, the contents of the entirety of which isincorporated by this reference. Other processes include U.S. Pat. Nos.4,401,823; 5,354,914; 6,291,725 and 6,479,713, each of the contents ofthe entirety of which are incorporated by this reference. U.S. Pat. No.6,479,713 describes a process including: substrates such as glycerol,sorbitol, xylitol, lactic acid, and arabinitol which are subjected tohydrogenolysis over a catalyst comprising Re—Ni supported on carbon at230° C. and 1300 psi hydrogen pressure to give two- and three-carbonglycols similar to those obtained from petrochemical-based feed stocks.In one example, after 1 hour, 25.3% glycerol conversion was achievedwith 72.3% selectivity to propylene glycol. The catalytic hydrogenolysisprocess may also involves a Nickel-on-alumina catalyst (C46-8-03 RS)obtained from United Catalysts Inc. (now Sud Chemie). This catalyst hadthe characteristics outlined in Table 4. TABLE 4 C46-8-03 RSHydrogenolysis catalyst characteristics Nickel (wt %) 48.9 SiO2 (wt %)4.59 Al2O3 (wt %) 30.3 Shape Cylindrical Average length (mm) 5.1 Averagecrush strength (lbs/mm) 1.8 Reduction (%) 43

The composition of the hydrogenolysis product mixture may be dependenton certain conditions, such as, for example, the particular bio-derivedpolyol feedstock or the hydrogenolysis process used. In a process (U.S.Pat. No. 6,479,713), mixed polyols were synthesized by feeding a 25%sorbitol solution into a reactor containing an alumina-based massivenickel catalyst (cylinder shaped) promoted with sodium hydroxide orsodium carbonate to 1% sodium. Over a period of 72 days, the feed(specific gravity, 1.1 g/mL, pH˜11.5) was fed into the reactor held at180-250° C. under 200-1800 psi pressure. A representative productcontained 47% propylene glycol, 20% ethylene glycol, 21% glycerol, andthe remainder was mixed diols.

Hydrogenolysis is a fixed bed catalytic process that uses hydrogen from1000-2000 psi, often at temperatures of 180-250° C. and typically isunder alkaline conditions. U.S. Pat. No. 6,479,713 describes a processwhere a nickel-rhenium-on-carbon catalyst was loaded into a 300-mLsemi-batch Parr reactor and purged with nitrogen. The catalyst wasactivated by adding hydrogen at 500 psi and heating to 280° C. for 16 hwith stirring. The reactor was cooled, the hydrogen removed, and 105.5 gof an aqueous solution of sorbitol (25%) and KOH (0.94%) was added. Thereactor was pressurized to 600 psi with hydrogen and heated; when thetemperature reached 220° C., the pressure was raised to 1200 psi. Thereaction was run for 4 h. Depending on the catalyst composition,sorbitol conversions ranged from 48.8 to 62.8%. In most cases, the majorproducts were glycerol, propylene glycol, and ethylene glycol. Otherfeed stocks tested included xylitol, arabinitol, lactic acid, andglycerol.

In U.S. Pat. No. 6,479,713, alditols (such as a 15-40 wt % sorbitolsolution in water) are catalytically hydrocracked in a fixed bedcatalytic reaction process using an active nickel catalyst to produce atleast about 30 W % conversion to glycerol and glycol products. The feedstream pH is controlled to between 7 and 14 by adding an alkali materialsuch as calcium hydroxide or a strong base such as sodium hydroxide toprevent damage to the catalyst. Useful prior art reaction conditions are400-500° F., 1200-2000 psig hydrogen partial pressure, and a liquidhourly space velocity of 1.5 to 3.0. To maintain desired catalystactivity and product yields, the catalyst is regenerated to providecatalyst age within the range of 20-200 hours. The reaction products areseparated in distillation steps at successively lower pressures, andunconverted alditol feed is recycled to the reaction zone for furtherhydrogenolysis to produce 80-95 W % glycerol product. Sorbitolconversion is maintained at between about 30-70 W % by catalystregeneration following 20 to 200 hours use, comprising washing to removedeposits and heating with hydrogen at 500-600° F. temperature.Countercurrent flow of feed and hydrogen in the reaction zone can beused if desired, particularly for achieving higher conversion of alditolfeed to glycerol products.

SUMMARY OF THE INVENTION

In one embodiment, a composition comprises a biobased propylene glycoland a weight/weight ratio of polyhydric alcohols other than propyleneglycol to the biobased propylene glycol of 0.5% or less.

In another embodiment, a composition includes a biobased propyleneglycol and polyhydric alcohols other than propylene glycol. In thecomposition, a ratio of the biobased propylene glycol to the polyhydricalcohols is between 100:1 and 1000:1

In a further embodiment, a system for producing biobased propyleneglycol comprises a conduit comprising a biobased glycerol containingsolution at a concentration of at least 30% glycerol and a reactor. Thereactor comprises a solid catalyst. The system further comprises asecond conduit comprising a biobased propylene glycol and polyhydricalcohols other than propylene glycol, wherein a weight/weight ratio ofthe polyhydric alcohols to the biobased propylene glycol is 0.5% orless.

In yet an additional embodiment, a process for producing biobasedpropylene glycol comprises placing a biobased glycerol containingsolution at a concentration of at least 30% glycerol by weight andhydrogen in contact with a solid catalyst such that the biobasedpropylene glycol is formed.

In yet another embodiment, a composition comprises polyhydric alcoholsobtained from a biobased feed stock. The polyhydric alcohols comprisepropylene glycol in an amount of at least 997 g/kg on a dry weight basisand 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol,2,4-pentanediol, ethylene glycol or any combinations thereof. The1,2-butanediol, the 1,3-butanediol, the 1,4-butanediol, the2,3-butanediol, the 2,4-pentanediol, the ethylene glycol or any of thecombinations thereof are present at a concentration of less than 0.5% ofthe propylene glycol concentration on dry weight basis

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block flow diagram illustrating one embodiment ofa process for producing value added bio-based products such as propyleneglycol and ethylene glycol from a bio-renewable feed stock such as aplant oil seed.

FIG. 2A is Table 5A.

FIG. 2 b is Table 5B.

FIG. 3 is Table 6.

FIG. 4 is Table 7.

FIG. 5 is Table 8.

FIG. 6 is Table 9.

FIG. 7 is Table 10.

FIG. 8 is Table 11.

FIG. 9 is Table 12.

FIG. 10 is one embodiment of a system for producing biobased propyleneglycol.

DETAILED DESCRIPTION OF THE INVENTION

The processes of the present disclosure provide methods for conversionof glycerol to useful derivatives and overcome the problems in currenttechnologies by producing value-added products including, but notlimited to, propylene glycol and ethylene glycol by hydrogenation ofglycerol feed stocks. In one embodiment, the present disclosure providesprocesses for conversion of crude glycerol into substantially purepropylene glycol.

In one embodiment, the present invention provides methods forhydrogenolysis of polyols which maximize the selectivity of the reactiontowards formation of propylene glycol and minimizes the formation ofother polyols. In one embodiment, the present invention disclosesprocesses for hydrogenolysis of glycerol which maximizes the selectivityof the reaction towards formation of propylene glycol and minimizes theformation of other polyols. In another embodiment, reaction conditionsare provided for different catalysts that can be applied to anyhydrogenolysis process for conversion of glycerol to propylene glycol.In one embodiment, selective formation of propylene glycol is obtainedwith little or negligible formation of other polyols that are difficultto separate by distillation, such as 1,2-butanediol and 2,3-butanediol.

In one embodiment, a process is provided for hydrogenolysis of glycerolcomprising placing glycerol in contact with hydrogen and a solidcatalyst at a liquid hourly space velocity of 0.5 hr⁻¹ to 10.0 hr⁻¹ tominimize formation of butanediols.

In another embodiment, the process for hydrogenolysis of glycerol whileminimizing formation of butanediols comprises adding a base.

In another embodiment, the process for hydrogenolysis of glycerol whileminimizing formation of butanediols comprises adding a base selectedfrom the group consisting of alkali metal hydroxides, alkoxides andbasic salts and alkaline earth metal oxides, alkoxides, hydroxides andbasic salts.

In another embodiment, the process for hydrogenolysis of glycerol whileminimizing formation of butanediols comprises adding a base in an amountfrom about 0.01 to about 2.5 weight percent of the glycerol solution.

In another embodiment, the process for hydrogenolysis of glycerol whileminimizing formation of butanediols comprises adding a base at a levelto maximize selective formation of propylene glycol over otherpolyhydric alcohols.

In another embodiment, the process for hydrogenolysis of glycerol whileminimizing formation of butanediols comprises adding a strong base isadded at 1-1.9 weight percent base.

In another embodiment, the process for hydrogenolysis of glycerol whileminimizing formation of butanediols comprises operating at a reactiontemperature of 178-205 degrees Centigrade.

In another embodiment, the process for hydrogenolysis of glycerol whileminimizing formation of butanediols comprises operating at a reactiontemperature of 176-193 degrees Centigrade.

In another embodiment, the process for hydrogenolysis of glycerol whileminimizing formation of butanediols comprises operating at a LiquidHourly Space Velocity of 1.5-2.3 hr⁻¹.

In another embodiment, the process for hydrogenolysis of glycerol whileminimizing formation of butanediols comprises hydrogenolysis of glycerolfrom fats or oils, comprising purifying a crude glycerol solution,bringing the glycerol solution in contact with hydrogen in a solutioncontaining a solid catalyst at a temperature between 100-220° C. and aLiquid Hourly space velocity of 0.5 hr⁻¹ to 2.5 hr⁻¹ to produce a streamof polyhydric glycols and fractionating the glycols stream.

In another embodiment, the process for hydrogenolysis of glycerol whileminimizing formation of butanediols comprises adding the strong base ata level to minimize formation of 1,3-butanediol and 2,3-butanediol.

In another embodiment, the process for hydrogenolysis of glycerol whileminimizing formation of butanediols comprises adding the strong base ata level to maximize selective formation of propylene glycol over otherpolyhydric alcohols.

In another embodiment, the process for hydrogenolysis of glycerol whileminimizing formation of butanediols comprises mixing a glycerolcontaining material with a base, to produce a hydrogenolysis precursormixture, subjecting the hydrogenolysis precursor mixture to a conditionthat allows propylene glycol to form, wherein the condition is selectedfrom the group consisting of liquid hourly space velocity, temperature,pressure, the presence of a catalyst and any combination thereof,wherein the propylene glycol is isolated and other polyhydric alcoholsare removed from the propylene glycol.

In a further embodiment, the process for hydrogenolysis of glycerol,while minimizing formation of butanediols, comprises the use of a theglycerol containing material that is selected from the group consistingof products of bio-diesel processing, petroleum processing, soapprocessing, fats processing, and mixtures of any thereof.

In a further embodiment, the process for hydrogenolysis of glycerol,while minimizing formation of butanediols, comprising associatingindicia with the propylene glycol to indicate that the propylene glycolhas a reduced content of other polyhydric alcohols.

According to certain embodiments, the bio-derived polyol feedstock canbe obtained by subjecting sugars or carbohydrates to hydrogenolysis(also called catalytic cracking). In one embodiment, sorbitol may besubjected to hydrogenolysis to provide a mixture comprising bio basedpolyols, as described herein (see, e.g. “Hydrogenolysis of sorbitol,”Clark, I., J. Ind. Eng. Chem. (Washington, D.C.) (1958), 50, 1125-6, thedisclosure of which is incorporated by reference herein in itsentirety). According to other embodiments, other polysaccharides andpolyols suitable for hydrogenolysis include, but are not limited to,glucose (dextrose), sorbitol, mannitol, sucrose, lactose, maltose,alpha-methyl-d-glucoside, pentaacetylglucose, gluconic lactone and anycombination thereof (see, e.g. “Hydrogenolysis of sugars,” Zartman, W.and Adkins, H., J. Amer. Chem. Soc. (1933) 55, 4559-63, the disclosureof which is incorporated by reference herein in its entirety).

According to other embodiments, the biobased polyol feedstock may beobtained as mixed polyols. Natural fibers may be hydrolyzed (producing ahydrolyzate) to provide bio-derived polyol feedstock, such as mixturesof polyols. Fibers suitable for this purpose include, but are notlimited to, corn fiber from corn wet mills, dry corn gluten feed whichcontains corn fiber from wet mills, wet corn gluten feed from wet cornmills that do not run dryers, distiller dry grains solubles (DDGS) andDistiller's Grain Solubles (DGS) from dry corn mills, canola hulls,rapeseed hulls, peanut shells, soybean hulls, cottonseed hulls, cocoahulls, barley hulls, oat hulls, wheat straw, corn stover, rice hulls,starch streams from wheat processing, fiber streams from corn mesaplants, edible bean molasses, edible bean fiber, and mixtures of anythereof. Hydrolyzates of natural fibers, such as corn fiber, may beenriched in bio-derived polyol feedstock suitable for use as a feedstockin the hydrogenation reaction described herein, including, but notlimited to, arabinose, xylose, sucrose, maltose, isomaltose, fructose,mannose, galactose, glucose, and mixtures of any thereof.

According to other embodiments, the bio-derived polyol feedstockobtained from hydrolyzed fibers may be subjected to fermentation. Thefermentation process may provide modified bio-derived polyol feedstocks, or may alter the amounts of residues of polysaccharides orpolyols obtained from hydrolyzed fibers. After fermentation, afermentation broth may be obtained and residues of polysaccharides orpolyols can be recovered and/or concentrated from the fermentation brothto provide a bio-derived polyol feedstock suitable for hydrogenolysis,as described herein.

According to certain embodiments, the hydrogenolysis product maycomprise a mixture of propylene glycol and ethylene glycol, along withminor amounts of one or more of methanol, 2-propanol, glycerol, lacticacid, glyceric acid, sodium lactate, and sodium glycerate. Severalbutanediols (BDO) such 1,2-butanediol, 1,3-butanediol, 1,4-butanediol,and 2,3-butanediol are produced in addition to 2,4-Pentanediol(2,4-PeDO).

In various embodiments, the hydrogenolysis product of the presentinvention comprising the biobased propylene glycol may be used in acomposition including, but not limited to, a deicer, an antifreeze, aresin, a laundry detergent, a soap, a personal care product, a cosmeticproduct, a pharmaceutical product, or as a food ingredient in afoodstuff or beverage.

Hydrogenolysis of bio-derived polyol feed stocks includes, but is notlimited to, polyol feed stocks derived from biological or botanicalsources. For example, bio-derived polyols suitable for use according tovarious embodiments of the present disclosure include, but are notlimited to: saccharides, such as, but not limited to, biologicallyderived (bio-derived) polyols including monosaccharides includingdioses, such as glycolaldehyde; trioses, such as glyceraldehyde anddihydroxyacetone; tetroeses, such as erythrose and threose;aldo-pentoses such as arabinose, lyxose, ribose, deoxyribose, xylose;keto-pentoses, such as ribulose and xylulose; aldo-hexoses such asallose, altrose, galactose, glucose (dextrose), gulose, idose, mannose,talose; keto-hexoses, such as fructose, psicose, sorbose, tagatose;heptoses, such as mannoheptulose and sedoheptulose; octoses, such asoctolose and 2-keto-3-deoxy-manno-octonate; and nonoses, such assialose; disaccharides including sucrose (table sugar, cane sugar,saccharose, or beet sugar) having glucose+fructose; lactose (milk sugar)having glucose+galactose; maltose (produced during the malting ofbarley) having glucose+glucose; trehalose is present in fungi andinsects, and is glucose+glucose; cellobiose is a glucose+glucosedisaccharide; oligosaccharides, such as raffinose (melitose),stachycose, and verbascose; sorbitol, glycerol, sorbitan, isosorbide,hydroxymethyl furfural, polyglycerols, plant fiber hydrolyzates,fermentation products from plant fiber hydrolyzates, and variousmixtures of any thereof.

As used herein, the term polyhydric alcohols may refer to a hydrogenatedform of a carbohydrate, where the carbonyl group (aldehyde or ketone)has been reduced to a primary or secondary hydroxyl group. The term mayalso be used to refer to glycerol, propylene glycol, ethylene glycol,sorbitol and/or BDO.

In one embodiment, the feedstock is glycerol. In an embodiment, theglycerol feed stock includes a diluent, such as water, or a non-aqueoussolvent. Non-aqueous solvents that may be used include, but are notlimited to, methanol, ethanol, ethylene glycol, propylene glycol,n-propanol and iso-propanol. Glycerol feed stocks are commerciallyavailable, or can be obtained as a byproduct of commercial biodieselproduction. According to other embodiments, the bio-derived polyolfeedstock may be a side product or co-product from the synthesis ofbio-diesel or the saponification of vegetable oils and/or animal fats(i.e., triacylglycerols). For instance, the glycerol feed stocks may beobtained through fats and oils processing or generated as a byproduct inthe manufacture of soaps. The feed stock may for example, be provided asglycerol byproduct of primary alcohol alcoholysis of a glyceride, suchas a mono-, di- or tri glyceride. These glycerides may be obtained fromrefining edible and non-edible plant feed stocks including withoutlimitation butterfat, cocoa butter, cocoa butter substitutes, illipefat, kokum butter, milk fat, mowrah fat, phulwara butter, sal fat, sheafat, borneo tallow, lard, lanolin, beef tallow, mutton tallow, tallow,animal fat, canola oil, castor oil, coconut oil, coriander oil, cornoil, cottonseed oil, hazelnut oil, hempseed oil, jatropha oil, linseedoil, mango kernel oil, meadowfoam oil, mustard oil, neat's foot oil,olive oil, palm oil, palm kernel oil, peanut oil, rapeseed oil, ricebran oil, safflower oil, sasanqua oil, shea butter, soybean oil,sunflower seed oil, tall oil, tsubaki oil, tung oil, vegetable oils,marine oils, menhaden oil, candlefish oil, cod-liver oil, orange roughyoil, pile herd oil, sardine oil, whale oils, herring oils, triglyceride,diglyceride, monoglyceride, triolein palm olein, palm stearin, palmkernel olein, palm kernel stearin, triglycerides of medium chain fattyacids, and derivatives, conjugated derivatives, genetically-modifiedderivatives and mixtures of any thereof.

Glycerol feed stocks are known to those of ordinary skill in the art andcan be used either in pure or crude form. The purity of United StatesPharmacopeia grade glycerol is greater than 99%. However, the purity ofthe glycerol having utility in the present invention may be between10-99% by weight. The glycerol may also contain other constituents suchas water, triglycerides, free fatty acids, soap stock, salt, andunsaponifiable matter. In one embodiment, the feed stocks may comprise20-80% by weight of glycerol.

Catalysts for the present hydrogenolysis processes are solid orheterogeneous catalysis. The catalysts may include those known in theart or as described herein. The catalysts are provided with a largesurface area support material that prevents degradation under thereaction conditions. These supports may include, but are not limited to,carbon, alumina, titania and zirconia, silica, or a combination thereof.These supports can also be prepared in mixed or layered materials suchas mixed with catalyst materials. The hydrogenolysis catalyst used inthe reaction may be a primary heterogeneous catalyst selected from thegroup consisting of palladium, rhenium, nickel, rhodium, copper, zinc,chromium or any combinations thereof. In one embodiment, a secondarycatalyst is used in addition to the primary metal catalyst. Secondarycatalysts may comprise additional metals, including without limitationnickel, palladium, ruthenium, cobalt, silver, gold, rhenium, platinum,iridium, osmium, copper and any combination thereof. In one embodiment,combinations of metals such as nickel/rhenium, copper/rhenium, andcobalt/rhenium may be employed. Alternatively, the catalyst may be ahomogenous catalyst, such as an ionic liquid or an osmonium salt whichremains liquid under the reaction conditions employed.

Catalytic hydrogenolysis can further comprise utilization of an addedbase. Assuming a neutral starting pH of a polyol feedstock, such assorbitol or glycerol, of from about pH 5 to about pH 8, an appropriatepH for catalytic hydrogenolysis can be achieved by, for example, anaddition an alkali, such as sodium hydroxide, to a final concentrationof from about 0% to about 10% by weight, or from about 0.5% to about 2%by weight, relative to the weight of the final solution. In some cases,the added strong alkali base has been referred to as a “promoter”. In anembodiment, the selectivity of the catalyst and yield of propyleneglycol (PG) can be improved by treating the reactant mixture to renderthe pH value neutral or alkali prior to or during the hydrogenolysisreaction, as well as carrying out the reaction under alkalineconditions. During the reaction, organic acids are formed whichneutralize the alkali added to the reaction. As the reaction proceeds,the pH is reduced, causing concomitant reduction in the selectivity ofthe catalyst. Methods are provided in the present disclosure to ensurethat the reaction is carried out in sufficient alkalinity to amelioratethis problem. In one embodiment, the reaction is conducted under alkaliconditions, such as at a pH 8 to 14, or at a pH of 10 to 13. These pHvalues may be obtained by adding an alkali, such as a strong base suchas sodium hydroxide. In embodiments, the sodium hydroxide could be addedto a level of 0.2 to 0.7%.

The temperature used in the hydrogenolysis reaction may range from 150°C. to 300° C. while the pressure is between 500 psi and 2000 psi, or1000 psi to 1600 psi. The reaction time for the hydrogenolysis reactionis defined by the term “weight hourly space velocity” (WHSV) which isthe weight of reactant per unit weight of catalyst per hour.Alternatively, the term “liquid hourly space velocity” (LHSV) may alsobe used, and is volume of reactant per unit volume of catalyst per hour.In an embodiment, a value for HSV is 1.8, which can be modified suitablyto meet reactor design specifications using techniques well known tothose in the art.

The compositions and methods disclosed herein are not limited to anyparticular hydrogenolysis procedures, reagents, or catalysts. Rather,the compositions and methods described herein may incorporatehydrogenolysis products from any known method.

Hydrogenolysis of a bio-derived polyol feedstock such as, for example, abio-derived polyol feed stock as described herein, results in ahydrogenolysis product. According to certain embodiments of the presentdisclosure, the hydrogenolysis product may comprise a mixture ofpropylene glycol and ethylene glycol containing minor amounts of one ormore of methanol, 2-propanol, glycerol, lactic acid, glyceric acid,sodium lactate, sodium glycerate, and combinations of any thereof.According to certain embodiments, the hydrogenolysis product maycomprise 0.1% to 99.9% by weight of propylene glycol, 0.1% to 99.9% byweight of ethylene glycol, 0.1% to 99.9% by weight of methanol, 0.10% to99.9% by weight of 2-propanol, 0.1% to 99.9% by weight of glycerol, 0.1%to 99.9% by weight of lactic acid, 0.1% to 99.9% by weight of glycericacid, 0.1% to 99.9% by weight of sodium lactate, and 0.1% to 99.9% byweight of sodium glycerate.

FRISA has established certification requirements for determiningbio-based content. These methods require the measurement of variationsin isotopic abundance between bio-based products and petroleum derivedproducts, for example, by liquid scintillation counting, acceleratormass spectrometry, or high precision isotope ratio mass spectrometry.Isotopic ratios of the isotopes of carbon, such as the ¹³C/¹²C carbonisotopic ratio or the ¹⁴C/¹²C carbon isotopic ratio, can be determinedusing isotope ratio mass spectrometry with a high degree of precision.Studies have shown that isotopic fractionation due to physiologicalprocesses, such as, for example, CO₂ transport within plants duringphotosynthesis, leads to specific isotopic ratios in natural orbio-derived compounds. Petroleum and petroleum derived products have adifferent ¹³C/¹²C carbon isotopic ratio due to different chemicalprocesses and isotopic fractionation during the generation of petroleum.In addition, radioactive decay of the unstable ¹⁴C carbon radioisotopeleads to different isotope ratios in bio-based products compared topetroleum products. Bio-based content of a product may be verified byASTM International Radioisotope Standard Method D 6866. ASTMInternational Radioisotope Standard Method D 6866 determines bio-basedcontent of a material based on the amount of bio-based carbon in thematerial or product as a percent of the weight (mass) of the totalorganic carbon in the material or product. Bio-derived and bio-basedproducts will have a carbon isotope ratio characteristic of abiologically derived composition.

Biology offers an attractive alternative for industrial manufacturerslooking to reduce or replace their reliance on petrochemicals andpetroleum derived products. The replacement of petrochemicals andpetroleum derived products with products and/or feed stocks derived frombiological sources (i.e., bio-based products) offer many advantages. Forexample, products and feed stocks from biological sources are typicallya renewable resource. As the supply of easily extracted petrochemicalscontinues to be depleted, the economics of petrochemical production willlikely force the cost of the petrochemicals and petroleum derivedproducts to higher prices compared to bio-based products. In addition,companies may benefit from the marketing advantages associated withbio-derived products from renewable resources in the view of a publicbecoming more concerned with the supply of petrochemicals.

Propylene glycol produced by the embodiments described herein isreferred to as “bio-based” propylene glycol. Propylene glycol producedas such finds many uses. Some of these include, but are not limited to,use as a solvent for aromatics in the flavor-concentrate industry; awetting agent for natural gums; an ingredient in the compounding ofcitrus and other emulsified flavors; a solvent in elixirs andpharmaceutical preparations; a solvent and coupling agent in theformulation of sunscreen lotion shampoos, shaving creams and othersimilar products; an emulsifier in cosmetic and pharmaceutical creams;an ingredient for low-temperature heat-transfer fluids, involvingindirect food contacts, such as brewing and dairy uses, as well asrefrigerated grocery display cases; a very effective humectant,preservative, and stabilizer in semi-moist pet food, bakery goods, foodflavorings and salad dressings; use as a dust suppression agent;solvents and compatibilizers for the many dyes, resins and inks used inmodern high-speed printing presses; surface lubricant in metal partmanufacture; as a raw material for dipropylene glycol phthalate; aplasticizer for polyvinyl chloride (PVC) resins; for use in the naturalgas processing industry; and to provide freeze-thaw protection invarious wax products to help prevent damaged caused by freezing.Propylene glycol is also used as the starting material for the synthesisof propylene glycol esters with sorbitol and/or fatty acids. Such usesare not limited or all inclusive and may be readily developed by thoseskilled in the art.

Various embodiments of the present disclosure relate to a bio-basedpropylene glycol and ethylene glycol. The products produced by theprocesses of the present invention produced by the hydrogenolysis ofbio-derived polyols and the products produced therefrom may bedifferentiated from petroleum derived products, for example, by theircarbon isotope ratios using ASTM International Radioisotope StandardMethod D 6866. Products produced from the product mixture of thehydrogenolysis product from a bio-derived polyol feedstock may have abio-based carbon isotope ratio ranging from 50% to 100. As used hereinthe term “bio-based carbon isotope ratio” includes a composition or acomponent of a composition having a carbon isotope ratio, as determined,for example, by ASTM International Radioisotope Standard Method D 6866,the disclosure of which is incorporated by reference herein in itsentirety, that is indicative of a composition including, in whole or insignificant part, of biological products or renewable agriculturalmaterials (including plant, animal and marine materials) or forestrymaterials [Method ASTM 6866].

The present invention has been described with reference to certainexemplary embodiments, dispersible compositions and uses thereof.However, it will be recognized by those of ordinary skill in the artthat various substitutions, modifications or combinations of any of theexemplary embodiments may be made without departing from the spirit andscope of the invention. Thus, the invention is not limited by thedescription of the exemplary embodiments, but rather by the appendedclaims as originally filed.

EXAMPLE 1

A series of studies were conducted in a 2000 ml high-pressure StainlessSteel 316 reactor. As described in FIG. 1, a solid catalyst similar tothe “G” catalyst disclosed in U.S. Pat. No. 6,479,713 or the “HC-1”catalyst available from Sud Chemie (Louisville, Ky.) was loaded in thereactor to a final volume of 1000 ml of catalyst. The reactor wasjacketed with a hot oil bath to provide for the elevated temperature forreactions and the feed and hydrogen lines were also preheated to thereactor temperature. A solution of a bio-based, substantially pure, 40%USP grade glycerol was fed through the catalyst bed at LHSV ranging from0.5 hr⁻¹ to 2.5 hr⁻¹. Hydrogen was supplied at 1200-1600 psi and wasalso re-circulated through the reactor at a hydrogen to glycerol feedmolar ratio of 5:1. In other embodiments, the hydrogen to glycerol feedmolar ratio may be between 1:1 to 10:1. Tables 5A and 5B in FIGS. 2A and2B describe the results with hydrogenolysis of 40% USP grade glycerolfeed. Between 47.7-96.4% of the glycerol was converted and between36.3-55.4% of propylene glycol was produced. In addition to propyleneglycol, the hydrogenolysis reaction produced 0.04-2.31% unwanted BDOs,which may present a problem for recovery of pure propylene glycol (Table6). The BDOs were measured using a known gas chromatography analysismethod.

EXAMPLE 2

Example 2 describes a method to reduce the formation of BDOs andmaximize the conversion of glycerol to propylene glycol with a solidphase catalyst such as the “G” catalyst as disclosed in U.S. Pat. No.6,479,713 or the “HC-1” catalyst available from Sud Chemie (Louisville,Ky.). Hydrogenolysis of a 40% solution of glycerol was carried outsubstantially as described in Example 1. Table 7 in FIG. 4 describes theconditions used in this Example, and discloses the products produced inthis Example.

EXAMPLE 3

Hydrogenolysis of a 40% solution of glycerol was carried outsubstantially as described in Example 1. The effect of the reactiontemperature at constant concentrations of alkali (sodium hydroxide) andconstant LHSV on the amount of BDO formed was investigated. Table 8 inFIG. 5 describes the conditions used in this Example, and discloses theproducts produced in this Example.

EXAMPLE 4

Hydrogenolysis of a 40% solution of glycerol was carried outsubstantially as described in Example 1. The effect of LHSV of the feedat constant concentration of alkali (sodium hydroxide) and constant onamount of BDO formed was investigated. Table 9 in FIG. 6 describes theconditions used in this Example, and discloses the products produced inthis Example.

EXAMPLE 5

Hydrogenolysis of a 40% solution of glycerol was carried outsubstantially as described in Example 1 except that 180 mL of Süd ChemieHC-1 catalyst was used. The effect of increasing temperature on BDOformation was investigated. Table 10 in FIG. 7 describes the conditionsused in this Example, and discloses the products produced in thisExample.

EXAMPLE 6

Hydrogenolysis of a 40% solution of glycerol was carried outsubstantially as described in Example 1 except that 180 mL of Süd ChemieHC-1 catalyst was used. Table 11 in FIG. 8 describes the conditions usedin this Example, and discloses the products produced in this Example.

EXAMPLE 7

Hydrogenolysis of a 40% solution of glycerol was carried outsubstantially as described in Example 1, except that 180 mL of SüdChemie HC-1 catalyst was used. Table 12 in FIG. 9 describes theconditions used in this Example, and discloses the products produced inthis Example.

Consequently, as is evident to those skilled in the art suitableconditions exist for hydrogenolysis of glycerol to propylene glycolwherein the yield of propylene glycol is maximized and the formation ofBDOs is minimized. Using the embodiments of this invention, one skilledin the art may practice this invention to operate a reactor system andobtain high yields of propylene glycol with low concentrations of BDOs.

The present invention has been described with reference to certainexemplary embodiments, biobased propylene glycol and uses thereof.However, it will be recognized by those of ordinary skill in the artthat various substitutions, modifications or combinations of any of theexemplary embodiments may be made without departing from the spirit andscope of the invention. Thus, the invention is not limited by thedescription of the exemplary embodiments, but rather by the appendedclaims as originally filed.

1. A composition, comprising: a biobased propylene glycol; and aweight/weight ratio of polyhydric alcohols other than propylene glycolto the biobased propylene glycol of 0.5% or less.
 2. The composition ofclaim 1, further comprising ethylene glycol at a concentration of lessthan 0.25%.
 3. The composition of claim 1, wherein the polyhydricalcohols are selected from the group consisting of 1,2-butanediol,1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2,4-pentanediol,ethylene glycol and any combinations thereof.
 4. The composition ofclaim 1, wherein the biobased propylene glycol is of a glycerol origin.5. The composition of claim 1, wherein the weight/weight ratio of thepolyhydric alcohols to the biobased propylene glycol of 0.25% or less.6. A composition, comprising: a biobased propylene glycol; andpolyhydric alcohols other than propylene glycol; wherein a ratio of thebiobased propylene glycol to the polyhydric alcohols is between 100:1and 1000:1.
 7. The composition of claim 6, further comprising ethyleneglycol at a concentration of less than 0.3%.
 8. The composition of claim6, wherein the biobased propylene glycol is of a glycerol origin.
 9. Asystem for producing biobased propylene glycol, comprising: a conduitcomprising a biobased glycerol containing solution at a concentration ofat least 30% glycerol; a reactor comprising a solid catalyst; and asecond conduit comprising: a biobased propylene glycol; and polyhydricalcohols other than propylene glycol, wherein a weight/weight ratio ofthe polyhydric alcohols to the biobased propylene glycol is 0.5% orless.
 10. The system of claim 9, wherein the reactor further comprises abase.
 11. The system of claim 10, wherein the base is selected from thegroup consisting of alkali metal hydroxides, alkoxides and basic saltsand alkaline earth metal oxides, alkoxides, hydroxides, basic salts, andcombinations of any thereof
 12. The system of claim 9, wherein thereactor further comprises hydrogen.
 13. A process for producing biobasedpropylene glycol, the process comprising: placing a biobased glycerolcontaining solution at a concentration of at least 30% glycerol byweight and hydrogen in contact with a solid catalyst such that thebiobased propylene glycol is formed.
 14. The process according to claim13, further comprising measuring a content of the propanediols in thepropylene glycol containing solution.
 15. The process according to claim13, wherein the biobased glycerol containing solution in placed incontact with the hydrogen and the solid catalyst at a Liquid Hourlyspace velocity of between 0.5 hr⁻¹ to 10.0 hr⁻¹.
 16. The processaccording to claim 13, further comprising placing a base in contact withthe biobased glycerol containing solution, the hydrogen and the solidcatalyst.
 17. The process according to claim 16, wherein the base isselected from the group consisting of alkali metal hydroxides, alkoxidesand basic salts and alkaline earth metal oxides, alkoxides, hydroxides,basic salts, and combinations of any thereof.
 18. The process accordingto claim 13, further comprising maintaining a reaction temperature ofbetween 178-205 degrees Centigrade such that the biobased propyleneglycol is formed.
 19. The process according to claim 13, furthercomprising: mixing an acylglycerol containing material with an alcohol,thus producing a biodiesel precursor mixture; subjecting the biodieselprecursor mixture to a condition that allows biodiesel and the biobasedglycerol containing material to form; and fractionating the biobasedglycerol containing material from the biodiesel.
 20. A composition,comprising: polyhydric alcohols obtained from a biobased feed stock;wherein the polyhydric alcohols comprise: propylene glycol in an amountof at least 997 g/kg on a dry weight basis; and 1,2-butanediol,1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2,4-pentanediol,ethylene glycol or any combinations thereof, the 1,2-butanediol, the1,3-butanediol, the 1,4-butanediol, the 2,3-butanediol, the2,4-pentanediol, the ethylene glycol or any of the combinations thereofbeing present at a concentration of less than 0.5% of the propyleneglycol concentration on dry weight basis.